Fang Yi, Cao Hua, Gong Xiaoyong, Chen Yanqing, Zhuang Yugang, Zhou Shuqin, Chen Yuanzhuo, Jiang Yimei, Ji Xiaopin, Peng Hu, Jing Xiaoqian
Emergency Department, Shanghai Tenth People's Hospital, Shanghai, China.
Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Front Oncol. 2022 Feb 9;12:797392. doi: 10.3389/fonc.2022.797392. eCollection 2022.
AF4/FMR2 family member 4 (AFF4) is a core component of super elongation complex (SEC) and regulates the transcription elongation of many genes. AFF4 depletion or amplification is associated with multiple cancers, but its role in colorectal cancer (CRC) has not been investigated so far.
qRT-PCR and Western blot analyzed AFF4 expression in the paired clinical CRC tissues. The patients' overall survival curve was determined using the Kaplan-Meier plotter. experiments, such as cell proliferation, migration, and invasion, were used to preliminarily ascertain the role of AFF4 in CRC. A CRC cell liver metastasis animal model was well established. Livers were harvested and examined histologically by a series of indicators, such as tumor nodules, liver weight, ALT/AST activity, and tumor cell identification by hematoxylin-eosin (HE) staining.
We firstly examined the expression of AFF4 in colorectal cancer and normal tissues by collecting paired CRC tissues and adjacent normal tissues, revealing that AFF4 was significantly downregulated in CRC patients and lower expression of AFF4 was correlated with poor prognosis. Next, we observed that presence or absence of AFF4 in CRC cells had no effect on cancer cell proliferation, while AFF4 depletion significantly promoted the migration or invasion of CRC cells . Furthermore, we confirmed that AFF4 deficiency enhanced the metastatic capacity of CRC cells . Mechanistically, we found that AFF4 upregulated the transcription of gene, which encodes E-cadherin and suppresses the epithelial-mesenchymal transition (EMT). Knockdown of AFF4 interfered with transcription, resulting in downregulation of E-cadherin expression and the progression of CRC. Moreover, restored expression could rescue the phenotype of CRC cells without AFF4.
Collectively, our data demonstrated that AFF4 served as a significant novel regulator of CRC transcriptional regulation and a potential effective therapy target for patients with CRC.
AF4/FMR2家族成员4（AFF4）是超级延伸复合物（SEC）的核心组成部分，可调节许多基因的转录延伸。AFF4缺失或扩增与多种癌症相关，但迄今为止其在结直肠癌（CRC）中的作用尚未得到研究。
采用qRT-PCR和蛋白质免疫印迹法分析配对的临床CRC组织中AFF4的表达。使用Kaplan-Meier绘图仪确定患者的总生存曲线。通过细胞增殖、迁移和侵袭等实验初步确定AFF4在CRC中的作用。建立了CRC细胞肝转移动物模型。收获肝脏并通过一系列指标进行组织学检查，如肿瘤结节、肝脏重量、ALT/AST活性以及苏木精-伊红（HE）染色鉴定肿瘤细胞。
我们首先通过收集配对的CRC组织和相邻正常组织，检测了结直肠癌组织和正常组织中AFF4的表达，发现AFF4在CRC患者中显著下调，且AFF4表达较低与预后不良相关。接下来，我们观察到CRC细胞中AFF4的存在与否对癌细胞增殖没有影响，而AFF4缺失显著促进了CRC细胞的迁移或侵袭。此外，我们证实AFF4缺陷增强了CRC细胞的转移能力。机制上，我们发现AFF4上调了一个基因的转录，该基因编码E-钙黏蛋白并抑制上皮-间质转化（EMT）。敲低AFF4会干扰该转录，导致E-钙黏蛋白表达下调和CRC进展。此外，恢复该基因表达可挽救无AFF4的CRC细胞的表型。
总体而言，我们的数据表明AFF4是CRC转录调控的重要新型调节因子，也是CRC患者潜在的有效治疗靶点。
